Trade-offs of organic amendment input on soil quality and crop productivity in saline-alkali land globally: A meta-analysis

Investigation toward the understanding of the influence of organic amendment input (OAI) on soil quality and crop productivity is essential for farmland management and sustainable development. A systematic review of 196 research articles was conducted focusing on the application of organic amendments to saline-alkali land, resulting in a dataset comprising 1425 pairs of observations for meta-analysis across various experimental types, crops, organic amendments, and soil layers. These findings indicated that OAI markedly strengthened the ecosystems of saline-alkali land. Specifically, (1) soil salinization was substantially reduced: soil electrical conductivity, pH, and salt content decreased by 23.6 %, 2.3 %, and 20.9 %, respectively, as compared with treatment without organic amendment, while cation exchange capacity increased by 22.7 %. (2) Soil nutrient levels substantially increased: OAI induced increases in the soil organic carbon, total nitrogen, total phosphorus, available nitrogen, available phosphorus, and available potassium content by 50.0 %, 55.1 %, 25.6 %, 31.3 %, 58.9 %, and 41.3 %, respectively. (3) Crop productivity increased: crop yield and aboveground biomass increased by 36.5 % and 46.2 %, respectively, under OAI. Furthermore, the results of our subgroup analyses of different organic amendments revealed that biochar, farmyard manure, and compost had superior comprehensive benefits for the saline-alkali land ecosystems as compared with other organic amendments. However, crop residues and biofertilizers were also widely used, increasing both soil quality and crop productivity. Given the global agricultural challenges faced by large-scale production on saline-alkali land, our study has critical implications for enhancing both the quality and systemic productivity of saline-alkali soils, offering theoretical guidance for future scientific inquiries aimed at identifying optimal strategies to strengthen ecosystem functions within these regions through the use of organic amendments.